Lean NOx trap (LNT) catalysts, also known as NOx absorbers, are being developed to enable lean burn engines to meet challenging global emission standards. Although these catalysts show promise, they also present a number of engineering challenges. For example, LNT catalysts may perform poorly at the low operating temperatures that are typical of present-day diesel engines. LNT catalysts have been found to reduce NOx insufficiently at low temperatures to provide the emission control needed to meet stringent emission standards for such vehicles.